The study - conducted by Doctor Young-Shin Kim, of the Yale Child Study Center and her colleagues in the U.S., Korea and Canada - identifies children not yet diagnosed and has the potential to increase autism spectrum disorder prevalence estimates worldwide.

ASDs are complex neurobiological disorders that inhibit a person’s ability to communicate and develop social relationships, and are often accompanied by behavioral challenges.

Published online today, the study reports on about 55,000 children ages 7 to 12 years in a South Korean community, including those enrolled in special education services and a disability registry, as well as children enrolled in general education schools. All children were systematically assessed using multiple clinical evaluations. This method unmasked cases that could have gone unnoticed. More than two-thirds of the ASD cases in the study were found in the mainstream school population, unrecognized and untreated.

The research team, including cultural anthropologist Roy Richard Grinker of George Washington University, took steps to mitigate potential cultural biases that could impact diagnostic practices and prevalence estimates. They also considered that more Korean children with ASD may be found in mainstream educational settings based on the design of the highly structured Korean educational system, which often includes 12-hour-long school days. Therefore Korean children with ASD may function at various levels in the Korean general population while not receiving special education services.

“While this study does not suggest that Koreans have more autism than any other population in the world, it does suggest that autism may be more common than previously thought,” said Grinker.

According to Kim, the study’s corresponding author, experts disagree about the causes and significance of reported increases in ASD, partly because of variations in diagnostic criteria and incomplete epidemiologic studies that have limited the establishment of actual population-based rates.

“We were able to find more children with ASD and describe the full spectrum of ASD clinical characteristics,” said Kim, assistant professor in the Yale Child Study Center. “Recent research reveals that part of the increase in reported ASD prevalence appears attributable to factors such as increased public awareness and broadening of diagnostic criteria. This study suggests that better case finding may actually account for an even larger increase.”

Kim said that while the current project did not investigate potential risk factors in this particular population, the study does set the stage for ongoing work to examine genetic and environmental factors contributing to the risk of ASD.

She also noted that the study is further evidence that autism transcends cultural, geographic, and ethnic boundaries and is a major global public health concern, not limited to the Western world.

“We know that the best outcomes for children with ASD come from the earliest possible diagnosis and intervention,” said Kim, whose co-investigator, Yun-Joo Koh of the Korea Institute for Children’s Social Development, reported that in response to the study findings, Goyang City, host of the Korea study, has courageously begun to provide comprehensive assessment and intervention services for all first graders entering their school system. “We hope that others will follow Goyang City’s example so that any population-based identification of children with ASD is accompanied by intervention services for those children and their families.”